1. Field of the Invention
This invention relates to photographic apparatus for controlling the opening and closing of a photographic shutter.
2. Description of the Prior Art
Conventional shutter mechanisms, such as that shown in U.S. Pat. No. 3,533,346, are designed to utilize the advantageous characteristics of springs to derive the opening movement of the shutter blades. Such springs provide both desirable consistency of dynamic performance as well as relatively high available energy. To operate the shutters, power is required and, in most applications that power is delivered to the springs by an energy storing cocking procedure through a solenoid actuated ratchet assembly, as in the above-mentioned patent, or through a hand-driven device such as a film advance lever.
With the advent of the miniature but fully automated camera, a need was developed for a correspondingly compact shutter assembly which would remain accurate while operating under relatively low power levels, i.e., the compactness of the shutter assembly foreclosed the use of relatively large, strong springs for driving the shutter blades. Such an assembly is shown in U.S. Pat. No. 3,882,522 wherein a stepper motor is used to sequentially move the shutter blades toward a fully open orientation and then the motor is energized in an opposite directional sense to reverse the direction of movement of the shutter blades and return them in steps to a closed orientation. By so stepping the blades into the open position, mass-accelerative forces are materially reduced thereby minimizing any overshoot at the time that the direction of movement of the blades is reversed.